Amplifier for coded train-control apparatus



G. w. BAUGHMAN 1,772,796 AMPLIFIER FOR CODED TRAIN CONTROL APPARATUS Aug. 127-19 30.

Filed Oct. 9, 1929 INVENTOR: V 7

' N- mm if Patented Aug. 12, 1930 UNITED STATES PATENT OFFICE GEORGE 'W. BAUGHMAN, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION 015' PENNSYLVANIA AMPLIFIER FOR CODED TRAIN-CONTROL APPARATUS Application filed October 9, 1929. Serial No. 398,385.

My invention relates to train control a paratus and particularly to apparatus of t e type comprising train carried governing means controlled by energy received from the trackway. 1 I In one type of apparatus referred to, an alternating train control current of commercialfrequency such for example, as cycles per second, is caused to flow in the track rails by a suitable generator located adjacent to the trackway of each track section and this current is periodically interrupted by any suitable form of interrupter to produce codes having distinctive characteristics. For example, different codes may be produced by interrupting the trackway circuit at different frequencies. This signal is picked up by a train occupying the section by means of a receiver comprising windings carried by the train in advance of the forward wheels thereof. These windings are disposed in inductive relation with the track rails so that thereis induced in said receiver an alternating current which is periodically varied at the frequency of the interruptions of the trackway current. This alternating induced current is then amplified and caused to operate governing means on the train according to the particular code being transmitted. My present invention has particular reference to apparatus for amplifying this induced current. I will describe one formof amplifying apparatus embddying my invention, and will then point out the novel features thereof in claims.

The single figure of the accompanying drawing is a diagrammatic view illustrating negative terminal of this battery is connected one form of my invention.

Referring to the drawing, the numerals 1.

and 1 designate the windings of a receiver carried on the train in advance of the forward wheels thereof and in inductive relation with the track rails. These windings are connected in series iii such manner that the voltages induced therein by alternating train controlling current in the track rails are additive. The windings l and 1 are connected through a condenser 2 with the primary winding 3 of an auto-transformer L in a circuit which is tuned to resonance at the frequency of the alternating train controlling current delivered by the original source in the track rails. The secondary circuit of the autotransformer L is also tuned to resonance at the same frequency by a condenser 4 and a re actor 5. This secondary circuit therefore forms a filter which offers its lowest impedance to currents of the frequency of the train controlling current.

The periodically varying voltages induced in the secondary of the auto-transformer L are amplified by a threeselement electron tube E. The filament of the electron tube E is supplied with current from a suitable source of potential, such as a battery 8, the negative terminal of which is connected with one terminal of the filament through the ballast lamp 6 and resistance 7 and the positive terminal of which is connected with the other terminal of the filament througha wire 9. One terminal of the secondary of the autotransformer L is connected with the grid of the electron tube E, and the other terminal of the auto-transformer is connected with the filament of the tube E through the ballast lamp 6, resistance 7 and a condenser 10. The

parts are so proportioned that the grid of the tube E is normally negative with respect 'to the filament, by an amount such that the normal plate current is quite small but still of a value sufficiently large so that the slope of the plate current grid voltage characteristic at this point, causes substantial amplification.

The electron tube E is also provided with a plate circuit including a suitable source of plate potential, such as a battery 11. The

produce variations of the same frequency in the plate current through primary windings 12 and 13 of transformers T and T respectively. I prefer to connect a condenser 1 1 across primary 13 to by-pass a portion of the alternating component of this varying plate circuit current. The secondary 15 of the transformer T is connected with the input terminals of a full wave rectifier 16, the output terminals of which are connected across condenser 10 in the grid circuit of tube E. This rectifier is connected in such manner that the current supplied by it to the condenser 10 makes the grid of tube E less negative with respect to the filament than would otherwise be the case. Secondary winding 17 of transformer '1 is connected directly with the operating winding of a polarized master train controlling relay 18.

\Vhen no current is being supplied to the receiver windings 1 and 1*, the plate current has a steady value which is of camparatively low magnitude due to the normal negative bias on the grid of tube E. At the beginning of an impulse of train controlling current, however, the alternating potential across condenser 4 produces pulsations of corresponding frequency in the plate circuit, these pulsations passing through condenser 14. around primary 13 of transformer T Furthermore, these pulsations induce in secondary 15 of transformer T an alternating potential which is rectified and applied to condenser 10. As previously explained this results in a sudden decrease in the negative bias of the grid of tube E, and produces a sudden and comparatively large increase in the plate current. The increase in plate current through primary 13 induces in secondary 17 a half cycle of one polarity which swings armature 19 to one extreme position. -When the trackway current is next interrupted, the termination of pulsations in the plate circuit discontinues the supply of rectified current to con denser 10, so that the grid potential suddenly returns to its original value. When this happens, the plate circuit in primary 13 of transformer T is suddenly decreased, and there is then induced in secondary 17 a half cycle of current of polarity opposite to that induced in this winding during an increase in the plate circuit, and relay 18 is energized to swing its armature 19 to the other extreme position.

It is apparent from the foregoing that when the track current is coded in the manner previously described, the master relay 18 will be actuated in synchronism with the interruptions. The relay 18 may be utilized to control governing means, not shown in the drawing, in any suitable manner.

The condenser 10 in series with the grid circuit serves as a convenient means for applying the rectified pulsating potential to the grid circuit, first, because it ofiers practically no impedance to the alternating potential from the filter circuit and second, becausev it tends to smooth out the wave form of the rectified potential. In other words the effect of the condenser 10 is comparable to that obtained by suddenly inserting a battery potential in the grid circuit.

The negative potential between the grid and filament of the tube E may be obtained by the use of a G battery or by the proper location of filament resistances.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, I claim is:

1. Train carried governing apparatus comprising means for receiving electrical energy from the trackway, an electron tube having the grid and filament thereof connected with said receiving means, two transformers, a plate circuit for said tube including the primaries of said transformers in series, means including a rectifier connecting the secondary of one transformer with the grid and filament of said tube, and a train controlling relay connected with the secondary of the other transformer.

2. Train carried governing apparatus comprising means for receiving electrical energy from the trackway, a condenser, an electron tube having the grid and filament thereof connected with said receiving means through said condenser, two transformers, a plate circuit for said tube including the primaries of said transformers in series, a rectifier for supplying energy from the secondary of one transformer to said condenser, and a train controlling relay connected with the secondary of the other transformer.

3. Train carried governing appartus comprising means for receiving electrical energy from the trackway, a condenser, an electron tube having the grid and filament thereof connected with said receiving means throu said condenser, two transformers, a plate circuit for said tube including the primaries of said transformers in series, a full wave rectifier having its input terminals connected with the secondary of one of said transformers and having its output terminals connected across said condenser, and a relay connected with the secondary of the other said transformer.

4. Train carried governing apparatus comprising means for receiving electrical energy from the trackway, a tube having the grid and filament thereof connected with said receiving means through said condenser, a transformer, a plate circuit for said tube including the primary'of said} transformer, a full wave rectifier-having its what means including condenser, an electron input terminals connected with the secondary of said transformer and having its output terminals conriected with said condenser, and means controlled in response to changes in the current in said plate circuit.

In testimony whereof I afiix my signature GEORGE W. BAUGH'MAN. 

